This invention relates to a method for inhibiting the growth of or killing microorganisms such as algae, bacteria, yeast and/or fungi in a recirculating water system, to treated recirculating water systems and to compositions and kits suitable for use in the method.
The water in many industrial and recreational recirculating water systems such as cooling towers, swimming pools, spas, ornamental ponds, plumbing, pipework and other surfaces and the like is susceptible to infection by microorganisms such as bacteria, algae, yeast and fungi. These organisms may be pathogens or potential pathogens. Thus, for safety reasons, it is highly desirable to control their growth by the addition to the water of sanitizing agents. It is also desirable for aesthetic reasons, to control the growth of non-pathogenic bacteria, algae, yeast and fungi, particularly the so-called xe2x80x9cnuisancexe2x80x9d algae, yeast and fungi which cause discoloration and/or staining of the water and surfaces in contact with the water
A variety of sanitising agents have been employed for controlling undesirable micro-organisms in recreational recirculating water systems. The most common sanitising agents provide free chlorine and/or bromine (typically at a concentration in the water of 1 to 5 ppm free halogen). Chlorine may be provided either directly as chlorine gas or sodium or calcium hypochlorite or via a chlorine release agent such as a chlorinated isocyanurate or chlorinated and brominated hydantoin. Chlorine may also liberated in situ by electrolysis of sodium chloride. Other sanitising agents which have been used in such systems include ozone, ozone forming chemicals, hydrogen peroxide, hydrogen peroxide forming chemicals, copper and/or silver salts which provide copper, silver or chelated copper ions (typically at a concentration in the water of 0.1 to 1.0 ppm), quaternary amines and polymeric biguanides, especially poly(hexamethylene biguanide) (hereinafter referred to as PHMB) which is typically used at a concentration in recreational water of 6-10 ppm. Systems employing ultra violet light have also been used to sanitise recirculating water. Sanitising agents are used at higher concentrations in industrial recirculating water systems and additional sanitising agents may be used including but not limited to 2-methylisothiazolinone, 5-chloro-2-methylisothiazolinone, benzisothiazolinone, 2-bromo-2-nitropropane-1,3-diol, 1,2-dibromo-2,4-dicyanobutane, methylene bisthiocyanate, 2-(thiocyanomethylthio)-benzothiazole, formaldehyde and formaldehyde release agents, glutaraldehyde, dibromonitrilopropionamide and bromo-hydroxyacetophenone or mixtures thereof.
Although these primary sanitising agents are very effective in controlling bacteria they do not always provide consistent control of the so called xe2x80x9cnuisancexe2x80x9d algae, yeast and fungi which can cause discoloration and/or staining of the water and surfaces in contact with the water.
Examples of xe2x80x9cnuisancexe2x80x9d algae which are found in swimming pools include eukaryotic and prokaryotic algae, for example green algae (e.g. Chlorella spp.), black algae (e.g. Phormidium spp.) and mustard algae (e.g. Eustigmatos spp.). Of these, we have found that mustard algae are particularly difficult to control, regardless of the type of primary sanitising agent used. They appear as slimy deposits attached to the pool sides and bottom, as well as in the plumbing and in the filter, and vary in colour from dark green to brown.
Examples of xe2x80x9cnuisancexe2x80x9d fungi (often referred to as mold) isolated from swimming pools include Aspergillus spp., Cladosporium spp., Mucor spp. and Paecilomyces spp. Paecilomyces lilacinus is the causative agent in so-called xe2x80x9cwater moldxe2x80x9d, xe2x80x9cpink moldxe2x80x9d and xe2x80x9cpink algaexe2x80x9d. P lilacinus can manifest itself as white, grey or pink slimy deposits that are found in niches such as under ladder steps, in skimmer and pump baskets, in filters and piping. P lilacinus is also found growing in recirculating water filters where it can have an adverse effect on the efficiency and lifespan of the filter media. In its mature form, the fungus can also attach itself to pool surfaces and cause chronic turbidity problems which are difficult to control.
Examples of common xe2x80x9cnuisancexe2x80x9d yeasts found in swimming pools include Saccharomyces and Candidia species.
The wide spread occurrence of xe2x80x9cnuisancexe2x80x9d algae and fungi has lead to the introduction of methods of controlling these persistent microbes such as dosing with larger amounts of the sanitiser, shock dosing with chlorine or the introduction of further sanitisers or additives such as chelated copper, copper sulfate, combinations of chlorine and ammonium sulfate, colloidal silver, linear and/or cyclic quaternary amine compounds and polyquaternary amine compounds. However, these methods and algicides/fungicides have shown only limited efficacy against the xe2x80x9cnuisancexe2x80x9d algae and fungi and can give rise to undesirable levels of foam, especially in re-circulating water systems such as spas. Furthermore, in some circumstances, the additives themselves (especially chelated copper and copper sulphate) can cause staining of surfaces in contact with the water.
Any agent to be added to a recreational water system to control bacterial growth and xe2x80x9cnuisancexe2x80x9d algae, yeast and fungi must meet a number of demanding performance criteria. These include:
a) an excellent toxicology profile;
b) reasonable solubility;
c) freedom from unpleasant taste;
d) odourless or free from unpleasant odours (post addition);
e) non-staining of the construction materials e.g. plaster, plastic;
f) stability to light;
g) stability to other additives present in the water (e.g. sanitisers, H2O2 and EDTA);
h) little or no effect on foaming; and
i) no adverse effect on water appearance e.g. discoloration or turbidity.
Thus, there is a need for a method of treating recirculating water systems to control not only the growth of pathogens, potential pathogens and other bacteria, but also the growth of those xe2x80x9cnuisancexe2x80x9d algae, yeast and/or fungi which persist in the presence of a primary sanitizing agent.
According to the present invention there is provided a method for inhibiting the growth of or killing microorganisms, particularly bacteria, algae, yeast, and/or fungi in a recirculating water system comprising adding to the water a polymeric biguanide and an adjuvant of the Formula (1) or a salt thereof: 
wherein:
R1 is an optionally substituted C8 to C12 or C18 to C22 alkyl group; and
R2 and R3 each independently is H or optionally substituted C1-4-alkyl.
The Adjuvant
The alkyl group represented by R1 may be a branched chain or more preferably a straight chain alkyl group. It is especially preferred that R1 is n-octadecyl or more preferably n-dodecyl.
When any of R2 and R3 is C1-4-alkyl it may be a branched chain or more preferably a straight chain alkyl group. Examples of suitable alkyl groups include ethyl, n-propyl, iso-propyl and especially methyl. It is preferred however that R2 and R3 are H.
The alkyl groups represented by R1, R2 and R3 may be substituted by one or more substituents which do not adversely affect the activity of the adjuvant when used in combination with a polymeric biguanide according to the present invention. Suitable optional substituents include hydroxy, aryl (especially phenyl), amino, C1-4-alkoxy, hydroxy-C1-4-alkoxy or halogen (especially Cl). It is preferred, however that R1, R2 and R3 are un-substituted.
The adjuvant is preferably sufficiently water-soluble to give a concentration thereof in the recirculating water system which is sufficient to inhibit the growth of or kill microorganisms such as bacteria, algae, yeast, and/or fungi present in the recirculating water system. When the adjuvant is added to a recreational recirculating water system such as a swimming pool or spa it is also preferable that the adjuvant has sufficient water solubility not to adversely effect the appearance of the water in the recirculating water system, for example water colour or clarity.
Preferably the adjuvant has a water-solubility of at least 1 ppm, preferably at least 2 ppm, especially at least 5 ppm more especially at least 50 ppm and particularly at least 100 ppm. The upper limit of the adjuvant""s water-solubility does not matter, although typically the adjuvant has a water-solubility below 100,000 ppm, more usually below 25,000 ppm.
The term xe2x80x9cppmxe2x80x9d means parts per million by weight. One may easily determine the water-solubility of an adjuvant in ppm because this is the same as the weight of adjuvant in milligrams which will dissolve in 1 liter of water at 20xc2x0 C. For example if 10 mg of adjuvant dissolves in 1 liter of water at 20xc2x0 C. the water-solubility is 10 ppm.
The solubility of many adjuvants is influenced by pH. In a recreational recirculating water system the pH is preferably in the range of from 6.5 to 9.0, more preferably from 6.8 to 8.5 and especially from 7.0 to 8.2. Accordingly the above mentioned preferred solubility of the adjuvant is the solubility in water at the pH of the recirculating water system.
The adjuvant is preferably added to the water system to give a concentration thereof in the range 0.1 to 30 ppm, more preferably 0.1 to 24 ppm, more preferably 0.5 to 15 ppm, especially 5 to 15 ppm and more especially 6 to 10 ppm. These preferred concentrations provide good protection against the growth of microorganisms such as bacteria and nuisance algae, yeasts and fungi. It is especially preferred that the concentration of adjuvant is less than 25 ppm, because we have found that in some circumstances a higher concentration of adjuvant can result in water turbidity.
In view of the foregoing preferences the adjuvant is preferably selected from the group consisting of dodecylamine, octadecylamine, N,N-dimethyloctadecylamine and salts thereof. It is especially preferred that the adjuvant is dodecylamine or octadecylamine or a salt thereof. More especially the adjuvant is dodecylamine or a salt thereof. Dodecylamine provides good protection against the growth of microorganisms such as bacteria and xe2x80x9cnuisancexe2x80x9d algae, yeast and/or fungi and does not affect water quality, particularly water clarity.
When the adjuvant is used in the form of a salt, the salt may be formed with any anion which does not adversely affect the activity of the adjuvant when used with the polymeric biguanide. Preferably, the salt is an acid addition salt, more preferably a water-soluble acid addition salt. The acid forming the salt may be an inorganic acid or an organic acid. When the acid is an inorganic acid it is preferably hydrochloric acid.
When the salt is formed with an organic acid, the acid may contain a phosphonic, phosphoric, sulphonic or sulphate group but preferably contains a carboxylic acid group. The organic acid may be aromatic but is preferably aliphatic, including alicyclic. When the organic acid is aliphatic, the aliphatic chain of the organic acid may be linear or branched, saturated or unsaturated, including mixtures thereof. Preferably, the aliphatic chain is linear and it is also preferred that the organic acid is an aliphatic carboxylic acid.
It is preferred that the organic acid contains up to 12, more preferably up to 6 carbon atoms excluding the acid group.
The organic acid may contain more than one acid group but it is preferred that only one such group is present.
The organic acid may be substituted by a halogen or particularly a hydroxy group.
Suitable aliphatic carboxylic acids from which the salt can be formed include acetic acid, propionic acid, butyric acid, valeric acid, pivalic acid and lauric acid. Suitable aliphatic di-carboxylic acids include oxalic acid, malonic acid, succininic acid and gluconic acid. Suitable hydroxy substituted acids include glycolic acid, lactic acid, glyceric acid, malic acid and tartaric acid.
The salts of the adjuvant may be formed using conventional methods, for example by reacting the compound of Formula (1) with the acid optionally in the presence of a solvent. The resulting salt may then be isolated by, for example evaporation. It is preferred that the resulting salt is purified prior to use in the present method to remove undesirable impurities.
A single adjuvant or two or more of the adjuvants may be used in the present method. The use of two or more of the adjuvants may advantageously provide a broader spectrum of activity than the use of a single adjuvant.
Polymeric Biguanide
The polymeric biguanide preferably contains at least two biguanide units of Formula (2): 
linked by a bridging group which contains at least one methylene group. The bridging group preferably includes a polymethylene chain, optionally incorporating or substituted by one or more hetero atoms such as oxygen, sulphur or nitrogen. The bridging group may include one or more cyclic moieties which may be saturated or unsaturated. Preferably, the bridging group is such that there are at least three, and especially at least four, carbon atoms directly interposed between two adjacent biguanide units of Formula (2). Preferably, there are not greater than 10 and especially not greater than eight carbon atoms interposed between two adjacent biguanide units of Formula (2).
The polymeric biguanide may be terminated by any suitable group, such as a hydrocarbyl, substituted hydrocarbyl or by an amine group or by a cyanoguanidine group of the formula: 
When the terminating group is hydrocarbyl, it is preferably alkyl, cycloalkyl, aryl or aralkyl. When the terminating group is substituted hydrocarbyl, the substituent may be any substituent which does not exhibit undesirable adverse effects on the microbiological properties of the polymeric biguanide. Preferred aryl groups include phenyl groups. Examples of suitable substituents are aryloxy, alkoxy, acyl, acyloxy, halogen and nitrile.
When the polymeric biguanide contains two biguanide groups of Formula (2), it is preferred that the two biguanide groups are linked through a polymethylene group, especially a hexamethylene group and the biguanide is a bisbiguanide.
The terminating groups in such bisbiguanides are preferably C1-10-alkyl which may be linear or branched and optionally substituted aryl, especially optionally substituted phenyl. Examples of such terminating groups are 2-ethylhexyl and 4-chlorophenyl. Specific examples of such bisbiguanides are compounds represented by Formula (3) and (4) in the free base form: 
The polymeric biguanide preferably contains more than two biguanide units of Formula (2) and is preferably a linear polymeric biguanide which has a recurring polymeric chain represented by Formula (5) or a salt thereof: 
wherein X and Y represent bridging groups which may be the same or different and in which together the total of the number of carbon atoms directly interposed between the pairs of nitrogen atoms linked by X plus the number of carbon atoms directly interposed between the pairs of nitrogen atoms linked by Y is more than 9 and less than 17.
The bridging groups X and Y preferably consist of polymethylene chains, optionally interrupted by hetero atoms, for example, oxygen, sulphur or nitrogen. X and Y may also incorporate cyclic moieties which may be saturated or unsaturated, in which case the number of carbon atoms directly interposed between the pairs of nitrogen atoms linked by X and Y is taken as including that segment of the cyclic group, or groups, which is the shortest. Thus, the number of carbon atoms directly interposed between the nitrogen atoms in the group 
is 4 and not 8.
The linear polymeric biguanides having a recurring polymer unit of Formula (5) are typically obtained as mixtures of polymers in which the polymer chains are of different lengths. Preferably, the number of individual biguanide units of formulae: 
is, together, from 3 to about 80.
The preferred linear polymeric biguanide is a mixture of polymer chains in which X and Y are identical and the individual polymer chains, excluding the terminating groups, are of the Formula (6) or a salt thereof: 
wherein n is from 4 to 40 and especially from 4 to 15. It is especially preferred that the average value of n is about 12. Preferably, the average molecular weight of the polymer in the free base form is from 1100 to 3300.
The linear polymeric biguanides may be prepared by the reaction of a bisdicyandiamide having the formula: 
with a diamine H2Nxe2x80x94Yxe2x80x94NH2, wherein X and Y have the meanings defined above or by reaction between a diamine salt or dicyanimide having the formula: 
with a diamine H2Nxe2x80x94Yxe2x80x94NH2 wherein X and Y have the meanings defined above. These methods of preparation are described in UK specifications numbers 702,268 and 1,152,243 respectively, and any of the polymeric biguanides described therein may be used.
As noted hereinbefore, the polymer chains of the linear polymeric biguanides may be terminated either by an amino group or by a cyanoguanidine group: 
This cyanoguanidine group can hydrolyse during preparation of the linear polymeric biguanide yielding a guanidine end group. The terminating groups may be the same or different on each polymer chain.
A small proportion of a primary amine Rxe2x80x94NH2, where R represents an alkyl group containing from 1 to 18 carbon atoms, may be included with the diamine H2Nxe2x80x94Yxe2x80x94NH2 in the preparation of polymeric biguanides as described above. The primary amine acts as a chain-terminating agent and consequently one or both ends of the polymeric biguanide polymer chains may be terminated by an xe2x80x94NHR group. These xe2x80x94NHR chain-terminated polymeric biguanides may also be used.
The polymeric biguanides readily form salts with both inorganic and organic acids. Preferred salts of the polymeric biguanide are water-soluble. When the polymeric biguanide is represented by a compound of Formula (3) in the free base form, a preferred water soluble salt is the digluconate. When the polymeric biguanide is represented by a compound of Formula (4) in the free base form, a preferred water soluble salt is the diacetate. When the polymeric biguanide is a mixture of linear polymers represented by Formula (6) in the free base form, the preferred salt is the hydrochloride.
It is especially preferred that the polymeric biguanide is a mixture of linear polymers, the individual polymer chains of which, excluding the terminating groups, are represented by Formula (6) in the hydrochloride salt form. This is commercially available from Avecia Inc. under the trademark BAQUACIL
The polymeric biguanide is preferably added to the re-circulating water system to give a concentration thereof in the water of from 1 to 20 ppm, more preferably from 4 to 15 ppm, especially from 5 to 12 ppm, more especially from 6 to 10 ppm.
We have found that a combination of a polymeric biguanide (especially PHMB) with an adjuvant of the Formula (1) or a salt thereof provides particularly effective control over the growth of bacteria and nuisance algae, yeast and fungi. Furthermore, the combination of the polymeric biguanide and adjuvant gives a fast rate of kill of undesirable micro-organisms. We have also found that the combination of adjuvant and polymeric biguanide exhibit a high residence time in the water, thereby providing long term protection against the growth of bacteria and nuisance algae. A long residence time is desirable because it reduces the frequency of re-dosing with the polymeric biguanide and/or adjuvant necessary to sustain protection in the recirculating water system.
As hereinbefore mentioned the polymeric biguanide and adjuvant may be added sequentially in any order. However, for ease of dosing it is preferred that they are added together as a composition comprising the polymeric biguanide, the adjuvant and optionally a carrier. The carrier, when present, may be a solid or a liquid medium and may comprise a mixture of one or more solids or liquids.
When the carrier is a solid it is preferably a solid which, when dissolved in the recirculating water system, does not have an adverse effect upon the water, such as discoloration of the water or causing turbidity. It is especially preferred that the solid is a water soluble solid, because this avoids the formation of undesirable deposits in the recirculating water system. Solid carriers which may be used include, but are not limited to kaolin, bentonite, kieselguhr, calcium carbonate, talc, powdered magnesia, china clay or more preferably a water soluble inorganic salt, or a filler conventionally used in the preparation of tablets, such as microcrystalline cellulose, lactose and mannitol.
When the carrier is a solid the adjuvant and polymeric biguanide may be simply mixed with the carrier to provide a powder formulation which can be added directly to the recirculating water system. Alternatively, the powder may be encapusulated in a water-soluble capsule, for example as is commonly used for encapsulating pharmaceuticals. This has the advantage that dosing of the powder is easily controlled, for example a single capsule can be filled with sufficient powder to give an effective concentration of the polymeric biguanide and adjuvant in the recirculating water system.
In an embodiment of the invention the polymeric biguanide and adjuvant may be used in the form of a tablet. Suitable tablet formulations include those commonly used for dispensing pharmaceuticals. The tablets may contain a number of components commonly used in the art of tablet formulation, for example, fillers, binders, and excipients.
When the carrier is a liquid medium, the composition is preferably a solution, suspension, emulsion, dispersion or micro-emulsion of the polymeric biguanide and adjuvant in the liquid medium.
The liquid medium is preferably water, a water-miscible organic solvent or more preferably a mixture of water and one or more water-miscible organic solvents.
Suitable water-miscible organic solvents include alcohols, preferably C1-6-alkanols, for example methanol, ethanol, propanol and isopropanol; diols, preferably diols having from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol; oligo- and poly-alkyleneglycols, for example diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol (preferably with an average Mn less than 1000, more preferably  less than 500) and polypropylene glycol (preferably with an average Mn less than 1000); triols, for example glycerol and 1,2,6-hexanetriol; mono-C1-4-alkyl ethers of diols, preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, for example 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; amides, for example N,N-dimethylformamide; cyclic amides, for example N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and 2-pyrrolidone; and sulphoxides, for example, dimethylsulphoxide; carboxylic acids, for example saturated and unsaturated aliphatic monocarboxylic or dicarboxylic acids for example methanoic, ethanoic, propanoic, butanoic, 2-methylpropanoic, pentanoic, 3-methylbutanoic, 2,2-dimethylpropanoic, dodecanoic, tetradecanoic, hexadecanoic, octadecanoic, ethandioic, propanedioic, butanedioic, pentandioic, hexanedioic, heptanedioic, octanedioic, nonanedioic, and decanedioc acid, unsaturated aliphatic acid for example propenoic, propynoic, 2-methylpropenoic, trans and cis-2-butenoic, trans and cis-9-octadecanoic, trans and cis-butenoic and cis-methylbutenedioic, C1-6-alkanols and C1-4 saturated carboxylic acids are particularly preferred. Especially preferred water-miscible organic solvents include acetic acid, propanoic acid and ethanol.
If the formulation is in the form of a suspension, dispersion or emulsion, it preferably also contains a surface active agent to produce a stable dispersion or to maintain the non-continuous phase uniformly distributed throughout the continuous phase. Any surface active agent which does not have a significantly adverse effect on the biocidal activity of the adjuvant and polymeric biguanide may be used. Suitable surface active agents include emulsifiers and surfactants and mixtures thereof. The emulsifiers/surfactants may by non-ionic, anionic or a mixture thereof. Suitable anionic emulsifiers and surfactants include alkylarylsulfonates (for example calcium dodecylbenzenesulfonate), alkylsulfates (for example sodium dodecylsulfate), sulfosuccinates (for example sodium dioctylsulfosuccinate), alkylethersulfates, alkylarylethersulfates, alkylether carboxylates, alkylarylethercarboxylates, lignin sulfonates or phosphate esters. Suitable non-ionic emulsifiers and surfactants include fatty acid ethoxylates, ester ethoxylates, glyceride ethoxylates (for example castor oil ethoxylate), alkylaryl polyglycol ethers (for example nonylphenol ethoxylates), alcohol ethoxylates, propylene oxide-ethylene oxide condensation products, amine ethoxylates, amide ethoxylates, amine oxides, alkyl polyglucosides, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylenesorbitol esters or alcohol ethoxy carboxylates, especially those obtainable from C12-14-alcohols.
The weight ratio of the polymeric biguanide:adjuvant may vary over wide limits, but in many embodiments is from 99:1 to 1:99, preferably from 4:1 to 1:4, more preferably from 1:2 to 2:1. It is especially preferred that the weight ratio of the polymeric biguanide to adjuvant is from 1:1 to 2:1.
Further improvements in the efficacy of the present method may be achieved by adding the adjuvant and polymeric biguanide to the recirculating water system in conjunction with one or more further antimicrobial compound(s). The addition of further antimicrobial compound(s) to the recirculating water system can provide a broader spectrum of antimicrobial activity and/or provide increased efficacy against particularly problematic algae, bacteria, yeast and/or fungi present in the recirculating water system. Furthermore, the combination of the adjuvant compound the polymeric biguanide and one or more further antimicrobial compound(s) may provide a synergistic effect.
The further antimicrobial compound(s) may possess anti-bacterial, anti-fungal, anti-algal or other antimicrobial activity. Suitable further anti-microbial compounds include agricultural fungicides, agricultural herbicides, algicides, sanitises, disinfectants or quaternary ammonium compounds and combinations thereof.
When the further antimicrobial compound is a sanitising agent the choice of sanitising agent will depend upon the recirculating water system in which it will be used. For recreational waters, suitable sanitising agents include for example chlorine, bromine, ozone, hydrogen peroxide, calcium hypochlorite, sodium hypochlorite, lithium hypochlorite, a chlorine release agent (preferably a chlorinated isocyanurate, or a chlorinated hydantoin, more preferably dichlorocyanuric acid or trichlorocyanuric acid), a bromine release agent, a hydrogen peroxide release agent, an ozone release agent or water-soluble copper or silver or chelated copper salts, (e.g. copper sulphate, chelated copper sulphate). In industrial recirculating water systems where the toxicity of the sanitising agent is not so important, other sanitisers may also be suitable for example 2-methylisothiazolinone, 5-chloro-2-methylisothiazolinone, benzisothiazolinone, 2-bromo-2-nitropropane-1,3-diol, 1,2-dibromo-2,4-dicyanobutane, methylene bisthiocyanate, 2-(thiocyanomethylthio)-benzothiazole, formaldehyde and formaldehyde release agents, glutaraldehyde, dibromonitrilopropionamide and bromo-hydroxyacetophenone or mixtures thereof.
When the further antimicrobial compound is a quaternary ammonium compound it may be a compound with a single quaternary ammonium group or a polyquaternary ammonium compound. Examples of suitable quaternary ammonium compounds include for example, N,N-diethyl-N-dodecyl-N-benzylammonium chloride, N,N-dimethyl-N-octadecyl-N-(dimethylbenzyl)ammonium chloride, N,N-dimethyl-N,N-didecylammonium chloride, N,N-dimethyl-N,N-didodecylammonium chloride; N,N,N-trimethyl-N-tetradecylammonium chloride, N-benzyl-N,N-dimethyl-N-(C12-C18alkyl)ammonium chloride, N-(dichlorobenzyl)-N,-N-dimethyl-N-dodecylammonium chloride, N-hexadecylpyridinium chloride, N-hexadecylpyridinium bromide, N-hexadecyl-N,N,N-trimethylammonium bromide, N-dodecylpyridinium chloride, N-dodecylpyridinium bisulphate, N-benzyl-N-dodecyl-N,N-bis(beta-hydroxy-ethyl)ammonium chloride, N-dodecyl-N-benzyl-N,N-dimethylammonium chloride, N-benzyl-N,N-dimethyl-N-(C12-C18 alkyl) ammonium chloride, N-dodecyl-N,N-dimethyl-N-ethylammonium ethylsulphate, N-dodecyl-N,N-dimethyl-N-(1-naphthylmethyl)ammonium chloride, N-hexadecyl-N,N-dimethyl-N-benzylammonium chloride or N-dodecyl-N,N-dimethyl-N-benzylammonium chloride.
In a preferred embodiment the further antimicrobial compound is a polyquaternary ammonium compound. Antimicrobial polyquaternary ammonium compounds which may be used include those described in U.S. Pat. Nos. 3,874,870, 3,931,319, 4,027,020, 4,089,977, 4,111,679, 4,506,081, 4,581,058, 4,778,813, 4,970,211, 5,051,124, 5,093,078, 5,142,002 and 5,128,100 which are incorporated herein by reference thereto.
Especially preferred polyquaternary compounds comprise a repeat unit of the Formula (7): 
wherein:
R4, R5, R6 and R7 each independently is C1-6-alkyl optionally substituted by hydroxy;
Q2xe2x88x92 is a divalent counter ion, two monovalent counter ions or a fraction of a polyvalent counter ion sufficient to balance the cationic charge in the repeat unit; and
a, b and t each independently is 1 to 4.
Preferably Q2xe2x88x92 is two monovalent anions selected from a halide anion and a trihalide anion, more preferably chloride or bromide.
R4, R5, R6 and R7 are preferably each independently C1-4-alkyl, more preferably methyl.
a, b and t are preferably each independently 1, 2 or 3. It is especially preferred that a, b and t are 2.
The polyquaternary ammonium compound with the repeat unit of Formula (7) preferably has a average molecular weight of from 1,000 to 5,000. An especially preferred polyquaternary ammonium compound with a repeat unit of Formula (7) is poly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylenedichloride). This polymer is commercially available under the Trademark WSCP from Buckman Laboratories Inc.
We have found that the use of a polyquaternary ammonium (especially poly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride)) in addition to the polymeric biguanide and adjuvant provides good protection against the growth of algae, especially those commonly found in recreational waters such as swimming pools. This combination is particularly useful as a remedial treatment for algal blooms in recreational waters.
When the further antimicrobial compound is a polyquaternary ammonium compound it is convenient to add the adjuvant and polyquaternary ammonium compound to the recirculating water system together as a formulation. Such formulations are commercially available, for example Busan 20/20(trademark) (ex Buckman Laboratories Inc.) is a formulation comprising poly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride) and a salt of dodecylamine.
Alternatively, the further antimicrobial compound may be added to the recirculating water system together with the adjuvant and polymeric biguanide together as a composition comprising optionally a carrier. The carrier, when present, may be a solid or a liquid medium. Suitable solid and liquid carriers which may be employed are as previously described. When a further antimicrobial compound is present in such a composition, the further antimicrobial compound typically comprises from 5 to 50%, and preferably from 10 to 30% by weight of the composition.
The Recirculating Water System
The invention is applicable to any industrial or recreational recirculating water system but is especially suitable for recreational recirculating water systems. Examples of industrial water systems include heating and cooling systems, e.g. cooling towers and domestic central heating systems. Examples of recreational recirculating water systems include swimming pools, spas and ornamental ponds. The invention is also applicable to plumbing, pipework and other surfaces which form part of the industrial or recreational recirculating water systems and which are susceptible to infection by microorganisms.